Main Highlights 

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• Energy is the capacity to do work
• The first law of thermodynamics states that energy is neither created nor destroyed
  • therefore, our bodies do not make energy
  • we consume food as an energy source, and then our bodies convert this food into usable energy in the form of ATP
    • this process is known as cellular respiration
• Metabolism - the sum of all chemical reactions in the body that are used to breakdown molecules or create molecules
  • metabolism is carried out by enzymes

• Why are enzymes important?

  • because without them the chemical reactions in our bodies would go too slowly to support life.
    • yes, the chemical reactions in our bodies would work without enzymes, but enzymes speed up these reactions so we don't die waiting.
• enzymes are known as biological catalysts
  • they speed up the rate of a reaction without being used up in the reaction
• Enzymes work by lowering the activation energy required for a reaction to take place
  • activation energy:
    • the amount of energy required to start a chemical reaction

• Lock and Key Hypothesis

  • enzymes work like a lock and key
    • each enzyme only has one substrate
    • the substrate fits into the the enzyme's active site 
      • active site is where in the enzyme molecule the reaction takes place
      • the active site is like the "lock" and the enzyme is like a "key"

• Induced Fit Hypothesis

  • this is an updated version of lock and key hypothesis
  • the lock and key hypothesis still exists
  • but scientists realized that the enyzme configures itself to mold to the substrate, ie. induced fit

• Substrate =

  • • reactant of enzyme-catalyzed reaction

• Product =

  • the end result of enzyme-catalyzed reaction

• Intermediate =

  • the in-between state of the reaction, where substrates are changing shape and structure

• Enzyme Naming

  • -ASE =

    • the ending of all enzymes
    • (except for the earliest discovered enzymes, like Pepsin, which is an enzyme that converts proteins to amino acids and does not end in -ase)
  • the prefix for all enzymes tells you about the action of the enzyme
    • e.g. ribonuclease = an enzyme that breaks apart RNA

• Optima

  • enzymes have temperature and pH optima that are very specific
  • Optima are the "best" conditions for an enzyme to function
  • Denaturation
    • an unfolding, weakened state of an enzyme that occurs when enzymes are not at their optima
  • When checking the temperature or pH optima of an enzyme, often a bell curve will result, where there is a peak of performance at the optimum

• Cofactors and Coenzymes

  • small molecules that help enzymes to function better

• Substrate and Enzyme concentration

  • if you increase the concentration of a substrate, the enzyme will produce more product up to a certain point.
    • this point is when the concentration of enzyme becomes rate-limiting.
    • the enzyme is re-used and continues to react with substrate
    • the enzyme cannot get to all the substrate because there's too much substrate
    • graph plateaus
  • if you increase the concentration of an enzyme, the enzyme will produce more product up to a certain point
    • this point is when the concentration of substrate becomes rate-limiting.
    • the enzyme runs out of substrate
  • linear range
    • the beginning of an enzyme-catalyzed reaction where neither substrate nor enzyme concentration is rate -limiting

• Metabolic pathways

  • our body is a maze of metabolic pathways
  • in a metabolic pathway, one enzyme forms a product, and the product of one reaction is the substrate for the next
  • Some metabolic pathways are branched, and the branch point is the key regulatory step.

• End Product inhibition

  • the end product of a metabolic pathway will stop the first reaction in the pathway (inhibit the first reaction in the pathway
  • this is negative feedback
  • allosteric inhibition
    • the product combines with the enzyme at a place that is different from the active site of the enzyme

• Inborn errors of metabolism

  • one gene codes for one enzyme
  • if there is a mutation in that gene, then the enzyme is not formed correctly and the product of the reaction does not form
  • e.g. Phenylketonuria (PKU) - mutation results in the inability to metabolize the amino acid phenylalanine (mental retardation can develop)
    • phenylalanine is part of aspartame, and so there is a warning on the label,
                        “not for phenylketonurics”
  • e.g. Gaucher’s disease and Tay Sach’s are lysosomal storage diseases (defective lysosomal enzymes that normally degrade lipids).

• ATP

  • the universal energy carrier
  • a lot of energy is released when the terminal phosphate is removed and ATP is converted to ADP
    • adenosine triphosphate is converted to adenosine diphosphate

• Coupled Reactions

  • exergonic reactions - release energy (break the phosphate off of ATP)
  • endergonic reactions - consume the energy released from the previous reaction

• REDOX reactions

  • concept: electrons are forms of energy 
  • oxidation reaction
    • electron is removed from a molecule
    • molecule is oxidized
  • reduction reaction
    • electron is given to a molecule
    • molecule is reduced
  • oxidation reduction reactions are coupled and are called REDOX reactions
  • one electron is taken from one molecule (donor molecule is oxidized) and given to the next molecule (recipient molecule is reduced)
  • the term “oxidation” does not refer to oxygen per se, but is used because oxygen          is electronegative and attracts electrons
  • electrons are often passed as Hydrogen ions because hydrogen is simply one proton and one electron.
    • a molecule that gains a hydrogen is reduced; sometimes gaining 2 hydrogen atoms

• NAD and FAD

  • function as hydrogen carriers (electron carriers)
  • FAD can accept 2 electrons and becomes FADH₂
  • NAD can also accept 2 electrons but can only bind one and is sometimes written as NADH + H⁺

• Video describing information from our book

• Video I made for high school students

  • (I know, I think I drank too much coffee before making this video :/ It's sad ).
    
    
    

• Good online resources You Tube

  • Bozeman Enzymes

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